A 25-year-old man pleaded guilty Monday to murdering his girlfriend’s baby girl last fall in this Red River Valley town.

Raul Perez of Dilworth admitted in Norman County District Court Monday that while taking care of 22-month-old Ariel Reyes on Aug. 29, he became angry when the child wouldn’t stop crying and threw her into her crib, said Norman County Attorney James Brue.

“His exact words were ‘I snapped,’” Brue said.

An autopsy found that the toddler died of neck and head injuries, according to court documents. Perez was watching the baby girl while her mother went to the grocery store.

Ariel Reyes died two days later at Sanford Medical Center in Fargo, where doctors noticed her chin, jaw, thigh, tailbone, forehead and armpits were all visibly bruised, according to court records.

Brue said he will be seeking a sentence of 20 years on the second-degree murder conviction, more than the state guideline – which is between about 11 and 15 years for an offender with Perez’s lack of a criminal history.

Despite Perez’s lack of a criminal record of note, Brue said he will ask for a longer sentence because the boyfriend was in a “position of trust or authority over the child” and because there was another young child, Ariel’s 5-year-old brother, present at the time of the crime.

His sentencing is scheduled for Sept. 9, after corrections officials conduct a presentencing report.

Perez last week fired his defense attorney, but he has since been granted a public defender, Eric Gudmunson, of the Polk County Public Defender Office in Crookston.